A computer disk, which is the most commonly used device to permanently store and retrieve data, comprises two principal components: a magnetic head (i.e., a transducing head) and a magnetic recording disk. The magnetic head writes data onto the magnetic recording disk through the change of the magnetic field in the magnetic head, which is caused by the change of the electric current that flows therethrough in accordance with the output signal from the central processing unit. On the other hand, the magnetic head also reads data from the magnetic recording disk, which induces a voltage in the magnetic head in accordance with the data that have been magnetically stored thereon. The voltage so induced is subsequently amplified and converted back into its original digital data form before it is transmitted to the central processing unit.
A magnetic recording disk typically comprises a plurality of tracks on which information is recorded or read out by sliding or flying a magnetic head over the surface of the magnetic disk along a circumferential path. With the proliferation and increased complexity of personal computers in handling a wide variety of tasks from desktop publishing to CAD, there is a great demand for magnetic disks with increased recording density.
The recording density of a magnetic recording medium is inversely proportional to the flying height of the magnetic head, with which the information is being recorded and read out. Consequently, in designing computer disks, the flying height of the magnetic head should be reduced as much as possible, in order to increase the recording density thereof. As such, the surface of the disk substrate should be extremely smooth to permit a lower flying height. However, the extreme smoothness of the disk also results in a high contact area between the disk and the magnetic head which, in turn, leads to a high degree of stiction and/or friction during the start up and the stopping of the disk. The high degree of stiction or friction can cause damage to the disk, the recording head and its accompanying assembly, as well as the disk drive motors. In order to alleviate these problems, a high wear resistance overcoat, such as amorphous carbon film, has been used which is deposited upon the magnetic film to protect the recording medium from incurring damage. In addition, various types of organic lubricant have also been applied onto the outermost layer to reduce the friction between the recording medium and the magnetic head. However, even an extremely smooth disk with a well designed lubricant coating can still exhibit unacceptably high levels of stiction and friction. To facilitate the retention of lubricant and thus lower the stiction and/or friction, a controlled surface topology, or the so-called "texture" is often required.
Texture also provides another purpose. Conventionally, in order to reduce undesirable stiction and friction, computer disk manufacturers often roughen the surface of the disk substrate by mechanical abrasive technique, known as texturing, in order that the magnetic head, when it slides across the landing area, contacts with a rough surface on the disk rather than a flat surface. This reduces the contact area between the magnetic head and disk surface, and thus result in a reduction of the stiction and friction therebetween. In the conventional mechanical texturing process, numerous small grooves or valleys are abraded on the disk surface.
The conventional disk texturing processes mentioned above use rotating pads or tapes with a circular motion to engage the rotating surface of the disk with a slurry that contains abrasives. The conventional mechanical texturing technique has several disadvantages in that, for example, it is usually associated with the formation of weldments and asperities along the texture lines. These weldments and asperities can result in an increase in the required flying height as well as severe wears on the magnetic layer during the operation of the disk. Typically, a 2.mu. flying height is perhaps the lowest height that can be achieved using the conventionally texturing technique. In the case of using rotating pads for disk texturing, it further has other disadvantages, including pad break-ins, short pad life, and difficulties in effectuating process automation.
Eur. Pat. App. No. 0 421 120 A2 discloses a magnetic storage medium prepared by depositing evaporated gallium films over a non-wetting silicon dioxide substrate at a temperature above the melting point of gallium, which forms many spherical structures or features. Thereafter, a Co--Pt--Cr alloy magnetic film layer is deposited over the gallium layer resulting in a reaction of gallium with the magnetic film. This method has several technological drawbacks and has not been commercialized utilized.
It is desirable to have a non-mechanical abrasive texturing process which not only provides improvements in the reduction of the flying height of the transducing head as well as the tribological characteristics of the magnetic recording disk and the controllability of the texture pattern, but also possesses the advantages in allowing process automation.